By Justin Parkinson BBC News education reporter, at the NASUWT conference

In a union survey some teachers said management took no action

Violent and disruptive pupils are making teachers' lives impossible and should be banned permanently from schools, teachers say.

Members of the NASUWT union voted unanimously to demand that parents should take more responsiblity for their children's actions.

One member of staff had been stabbed with a compass and several spat at, its annual conference heard.

Primary school pupils were sometimes as bad as those at secondary schools.

Punched and slapped

Delegates voted for pupil referral units - which deal with excluded children - to receive more funding.

David Ward, from Sheffield, told the conference some staff in mainstream secondary schools had been punched and slapped on the head.

Pupils had spat on teachers' heads from three floors up.

A small survey carried out by the NASUWT in eastern England suggests the level of violence and disruption among pupils reaches a peak towards the end of secondary school.

Among the members who responded, an assault - verbal or physical - was reported every nine minutes.

Parents

A spokesperson for the Education Secretary, Ruth Kelly, said she had made it clear she would back head teachers who acted to tackle bad behaviour - and was committed to "zero tolerance" of disruption in schools.

But a quarter of those who had reported incidents to school managers said no action was taken.

Mike Wilson, a teacher from Nottinghamshire, told the conference secondary school pupils were not the only disruptive ones.

He told the conference in Brighton that those in primary schools also suffered from an "it's-not-fair syndrome".

Mr Wilson added: "At five or six they are just as bad as when they are 10. The big difference is they are not as aggressive as when they are 10."

He asked parents to take more responsibility for disruptive pupils, rather than expecting staff to deal with all problems.

He said: "Can anyone find me a teacher who actively encourages his child to misbehave in the classroom?"

'Sugar effect'

Joy Higgins, a maths teacher from Chelmsford, Essex, called for a ban on all junk food in schools and colleges.

The "sugar effect" meant children's behaviour worsened after eating sweets and cakes during breaks.

She said: "By afternoon registration, I might as well just talk to myself and count heads."

Of one male pupil, she added: "One tutorial period, he came back and he was bouncing off the walls.

"I thought he had been on drugs, but he said he had had three doughnuts at break time."

There was more legislation on pet food than on dinners and snacks sold within schools, Ms Higgins said.

She added: "If we feed them rubbish, their behaviour reflects that rubbish."

But the union's executive opposed Ms Higgins' amendment on food and it was rejected by delegates.

The NASUWT, with 223,000 members, is the second biggest education union in the UK. Its conference lasts until Friday.